This invention relates to a seal and more particularly to a radial lip type seal, including a labyrinth therein, for sealing relatively rotatable members such as, but not limited to, joints in crawler tractor track linkage, hydraulic motor cylinder trunnions and various lever systems generally characterized as subject to oscillatory motion.
One prior art patent U.S. Pat. No. 2,750,214 discloses a two-piece seal wherein sealing is effected between the two pieces. Although some similarity may be apparent with reference to this prior art and the present disclosure, it will be seen from a description hereinafter set forth that substantial distinction exists therebetween.
Further prior art specifically relating to radial lip type seals, sometimes referred to as "wiper type" seals, may be found in various seal industry sales brochures and engineering manuals. For example, catalog 457010 issued May 1975 by the Chicago Rawhide Manufacturing Company, 900 North State St., Elgin, Illinois 60120 illustrates on pages 52, 53 and 54 many types and styles.
The environment under which seals operate in the before mentioned installations is generally recognized as being extremely severe. For example, track link joints of track-laying machines are exposed to ground surface conditions varying from dry dust and sand to mud slurry. These are usually very abrasive materials which may penetrate through the seal causing accelerated wear of the joint bearings resulting in machine downtime periods and costly repairs. Many prior art seals for track link joints are of the face type in which a seal element is urged axially into sealing contact by a resilient element against a joint member face. In this type of seal, as well as in prior art radial lip type seals, a barrier against entrance of damaging materials is provided by a single sealing medium wherein the seal element, a radial lip or an axial face, bears against a relatively rotating member usually a shaft or a track bushing end. In either case the relative motion in combination with abrasive materials tends to cause grooves to wear in these members thereby resulting in shorter than desired effective life of the sealing capability and a requirement to frequently replace expensive components.
The present invention represents a substantial improvement over the prior art because it includes a plurality of sealing mediums rather than a single medium. Further, the sealing action wear resulting from one relatively rotating member with another is between the two elements of the seal rather than between a seal element and a relatively expensive shaft or a member such as a track bushing. The importance of this is emphasized when considering the fact that some machines are composed of as many as a hundred and fifty seals subjected to the above mentioned kind of service.